This project will propose to study the mechanism of Fas-mediated cell death. Because ligation of the Fas molecule results in the rapid activation of acidic sphingomyelinase (aSMase), which hydrolyzes sphingomyelin into ceramide. a candidate intracellular messenger leading to cell death, we hypothesize that aSMase is functionally linked to Fas-mediated cell death. To prove (or disapprove this hypothesis, we will determine whether 1) aSMase activity correlates with Fas-mediated cell death, 2) the "death domain", a cytoplasmic region of the Fas molecule necessary for Fas-mediated cell death, is required for aSMase activation and 3) aSMase is inhibited by FAP-1, which is protein known to inhibit Fas-mediated cell death by binding to the cytoplasmic "inhibitory domain" of the Fas molecule. We anticipate that we will demonstrate that aSMase activation is necessary for Fas-mediated cell death, but activation of aSMase does not necessarily result cell death. The reason, we believe, is because while activation of the sphingomyelin pathway sends a signal for the induction of cell death, other additional signals (e.g via costimulation of CD4O, p55 TNFR, or CD28.) are either required or inhibited in order to result finally in cell death. The system, which we will develop, will allow us to systematically and individually study the mechanism by which these additional signals regulate and modify the Fas-mediated death signal. The award will essentially advance my career by providing additional training in the molecular mechanism of programmed cell death. With my previous background in mucosal immunology, the additional training will allow me to acquire the knowledge and skills to adequately investigate the role of programmed cell death as it relates to the intestinal immune system. Over the course of the next five years, I hope to be scientifically productive, obtain enough preliminary evidence to submit my first R01 and secure my first tenured track faculty position at a major biomedical research institute. The MCSDA Award will essentially provide salary support for the next five years of additional research experience.